Coasters Safty Brakes

Wednesday, April 16, 2003 2:37 PM
The other day I was at Lagoon in Utah and one of the cars on their new ride The Spider stalled/valleyed between one of the hills. I thought to my self how safe are the safty brakes? This would be awful if the cars collided and could you really trust the computer control systems?

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F.T.B.S.I.T.T.T.D.

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Wednesday, April 16, 2003 3:07 PM
1.) The brakes are very safe.

2.) The PLC is very safe.

But neither are failsafe.

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Is that a Q-bot in your pocket or are you just happy to see me?

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Wednesday, April 16, 2003 3:10 PM
Mike - Spider's track is divided into zones, called "blocks." A set of brakes separates each block. After a car passes a set of block brakes they close, preventing any other cars behind it from entering that section of track until the one occupying it crosses into the next block.

And yes, you can trust the computers. I'm sure the ride is safe.

Moosh

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"God bless Atheists!" - Homer Simpson


*** This post was edited by Mamoosh 4/16/2003 7:11:30 PM ***

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Wednesday, April 16, 2003 4:08 PM
Yes you can trust the computers... they're not gonna laugh and say "Lets crash these cars, ha ha ha!"
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God wants spiritual fruits, not religious nuts!
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Wednesday, April 16, 2003 4:26 PM
PLCs are very safe, The brakes are pretty much failsafe.

For further expalnaitions on Block systems please visit Ridemans webpage on Blocking
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So you believe that you are studying us, then kindly explain why you are the ones trapped in your seats.


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Wednesday, April 16, 2003 7:19 PM
I was just going to suggest a visit to my web page but I see FoF beat me to it...

The basis of any blocking system is that--

a) The entire track is divided up into blocks such that a ride vehicle can be RELIABLY stopped in any block.

b) The Rule™ of ride blocking systems is followed. The Rule™ is very simple, and can be summed up as follows:



Thou shalt not allow more than one train to occupy any block, at any time, for any reason, lest thy trains collide resulting in much wailing and gnashing of teeth.

In most cases, the blocking is handled first by lift hills, anti-rollback devices, and gravity: if the lift stops, gravity both prevents the train from proceeding and in combination with the anti-rollback device, prevents it from going back to the previous block. Second, coasters have brakes which are generally designed to be as failsafe as practical. This usually means redundant brake units, redundant brake air supplies, brakes that are set with gravity or with springs and released with air pressure, or combinations of those kinds of systems.

--Dave Althoff, Jr.

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Wednesday, April 16, 2003 10:07 PM
Programmable Logic Controllers [PLCs} have almost NOTHING in common with the computer your using right now. They are designed to be redundant where PC's and Windows are designed for compatibility to a multitude of programs.

Basically a PLC is an electronics device that takes a number of inputs then processes it within its predefined architecture. The PLC then controls the output devices when conditions are set for a given operation. Most electrical devices are designed to keep on running, but PLC controlling rides are structured in such a manner than any failure will cause the ride to go down until the situation is resolved.

The Rule™ has an exception.


Thou shalt not allow more than one train to occupy any block, at any time, for any reason, lest thy trains collide resulting in much wailing and gnashing of teeth.

Unless the speed and position of the trains are controled in a specified area.

Wildcat and Millennium Force fail The Rule™ without a restriction.



*** This post was edited by SteelMonsters 4/17/2003 2:12:51 AM ***

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Thursday, April 17, 2003 5:19 AM
It isn't really an exception to The Rule™. Well, Wildcat violates The Rule™ in the station, and you can see the results of that: the cars collide in the station on a continuous basis. On Millennium Force, though, the tactic is a little different. The station is actually divided into a fair number of overlapping blocks so that, so far as the controls are concerned, a train parked in the station may be occupying five or six blocks all at once, and as the departing train checks out of each block, the next train can be moved up. It's actually slightly more complex than that because the trains are driven through with kicker wheels. Another complication is that the first block beyond the station has a check-in point that moves downtrack as the train is dispatched, because the lift catchwagon can only be engaged at one position. So as the catchwagon pulls the train out of the station, technically, the train moving in from unload physically cannot enter the departing train's block once the departing train gets onto the anti-rollbacks. You can drop the drive wheel and push, but the train won't go up the hill until the catchwagon comes back. So Millennium Force does some funny things that look like Rule™ violations that really aren't.

In other points...
Functionally, the easiest way to think of a PLC is in terms of a set of virtual relays. In real-time, input switches are used to determine the settings for output signals. In block control systems, PLCs are mostly used to replace hard-wired relay control logic that was developed as early as the 1920's (the Riverview Park Bobs apparently had a fully automatic electric control system). And some modern coasters have a dirty little secret: I once had an opportunity to tour the Serial Thriller at Geauga Lake. While that ride does have an Allen-Bradley PLC on it, the PLC performs monitoring functions while the safety system is controlled by hard-wired relay logic.

--Dave Althoff, Jr.

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Thursday, April 17, 2003 7:21 AM
Nothing is failsafe. Although, I don't worry for my safety on coasters.

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Is that a Q-bot in your pocket or are you just happy to see me?

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Thursday, April 17, 2003 8:07 AM
To an engineer, failsafe simply means that the normal failure mode is to a safe condition. It doesn't mean "completely safe". For example, if the air supply to the brakes fails, springs close them. If the power to the PLC fails, all the brakes close shutting down the ride.

Nothing in life is completely safe. Even inactivity. People have been struck by meteorites while in their beds. Televisions and beds kill more people than rollercoasters.

There is currently a debate going on in the controls community on hard wired vs. programmed safeties. The hard wired school says the hard wire logic is more reliable. The programmed school says that hardwired logic is subject to the same programming errors as the ladder logic in a PLC. (Basically relays are programmed by the wire used to connect them) They also point out that the sensors are far more likely to fail and cause and accident than either relays or PLCs. (For technical reasons roller coaster sensors are a bit less prone to dangerous failures than many industrial sensors)

Consign AG who does the controls for B&M and GCI has a superb safety record using dual PLCs that have to agree or the ride is shutdown.

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Thursday, April 17, 2003 8:41 AM
Then there is the whole problem of whether the alleged 'safe' condition really is. Obviously collisions have happened on coasters with control systems which are not only designed to fail safe, but which are designed to a more stringent standard than The Rule™ requires...specifically, "Thou shalt always maintain either a lift hill or a vacant, closed brake between thy trains.". I guess it is rooted in a DIN standard, but it's the corporate design policy for a Major Amusement Park Chain. And yet, a coaster with controls designed around that rule managed to have a station collision. The reason is that a sensor failed, the control system lost track of one of the trains, and failed to what it thought was a safe condition...setting the brakes, not allowing the "front" train to advance, thus causing it to get rear-ended by the other train which the computer "thought" was in a different block.

Note that it wasn't a logic failure nor a relay failure. It was a check-out sensor failure.

It's also worth noting that in many cases, the PLC outputs are used to drive relays to actually operate the solenoid valves on the brakes. So programmed safeties are still subject to hard-wire equipment failures. The question is, which system is easier for an Unauthorized Person to alter?

Technically, I think the only thing that *must* be hard-wired is the E-stop relay......

--Dave Althoff, Jr.

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Thursday, April 17, 2003 9:01 AM
geez....do u really think the brakes are timed or something? the trains wont crash trust me. i would explain it to u if i wouldnt get into trouble for it, but i will so i will keep quiet.
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Thursday, April 17, 2003 9:17 AM
arockam,

Who are you referring to in your post? Please don't tell me you're trying to slam Rideman...he has more coaster engineering knowledge than you could ever hope to fit in your brain....

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--George H
---Superman the ride...coming to a SF park near you soon...
Currency tracking experiment... http://www.wheresgeorge.com (Referring to The "George" on the $1 bill - Not Me)

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Thursday, April 17, 2003 9:21 AM
Arockam,

Surely you must realize how foolish you sound. We have Rideman giving full technical details regarding the subject, and we have you saying, "dood ur such a lamer u no da trainz wood never crash ne way haha." Please, spare us.

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SRM 2003-Look for the guy with my name on his chest

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Thursday, April 17, 2003 9:28 AM
awwww, c'mon guys....it might not be chock full of technical knowledge, but there's good entertainment value....I always love when someone tries to tell Dave he doesn't know what he's talking about....:)

Based on my *considerable* experience here, Dave is always pretty quick to say when he isn't sure of something or is taking an *educated* guess...the rest of the time, it's best to read and absorb what you can....;)

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Acronymphomania (n): the socially unacceptable love of heights, and acronyms
Thanks for the memories #23...there is NO "next Jordan"

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Thursday, April 17, 2003 9:39 AM
Can anyone explain how arockam2 would 'get in trouble' for explaining how 'the trains won't crash?' I'm a smidgen confused.

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-Vater
Have you ridden a Toboggan?

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Thursday, April 17, 2003 9:39 AM
'gator, was it you that said "Be polite and ignore the idiots"? :) This guy's been stirring up trouble since last night (the only thread remaining is in the Suggestions forum).

Anywho, question... if the owner has the ride designed for the empty block rule (The Rule(tm) Corrollary A), wouldn't the missing train have stopped in the block (3) between the station (1) and where the system thought it was (2) as soon as the system "saw" that the train was in block 3?

On a humorous side note referring to SOOperGIR's laughing computer comment...perhaps someday this scenario would play out (WARNING: Overused Movie Reference coming up)...

RideMan opens up the case on the HAL CoasterComputer 2000 (which was created using spare parts from an old Translatatron 3000) after HAL quit playing by The Rule(tm):

"What are you doing, Dave? This is highly irregular..."
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Spring has arrived in Ohio...the Orange Barrels are blooming

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Thursday, April 17, 2003 9:43 AM
Don't worry Vater, nobody could be more confused than arockam2 is... ;)

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--George H
---Superman the ride...coming to a SF park near you soon...
Currency tracking experiment... http://www.wheresgeorge.com (Referring to The "George" on the $1 bill - Not Me)

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Thursday, April 17, 2003 9:56 AM
Jimmybob, in the incident Rideman refers too, wet skid brakes contributed. On a dry day, the scenario you outlined should have played out.
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Thursday, April 17, 2003 10:42 AM
Actually, I hadn't thought of THAT incident, but rather an earlier incident. Same park chain, different park, all caliper brakes. The computer did what it was supposed to, which was correct based on the information it had to work with.

The wet skid brakes...they had an even more conservative block plan for that one, but there is a rumor that there might have also been some operator error involved, as that ride was partial manual control at the time of the collision.

Are u guyz shure r friend arockam2 wuz referring 2 me? Cuz b-sides not m8king sense, hiz p0st l@@ked like it wuz referring 2 M1k3's 0riginal ? ... :)

--Dave Althoff, Jr.

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